The present invention generally relates to a system and method for moving a first fluid using a second fluid. More specifically, the present invention relates to system and method for moving a first fluid using a ferrofluid attracted by an electromagnetic field. The electromagnetic field may be generated by an electromagnetic source connected to a conduit, and the first fluid may move through the conduit. In an embodiment, the first fluid may absorb heat from a heat source and transfer the heat to a heat sink.
Integrated circuits dissipate heat which may prevent or may hinder operation. More powerful or more sophisticated integrated circuits, such as, for example, integrated circuits with a higher processing speed, typically dissipate more heat than less powerful or less sophisticated integrated circuits; accordingly, powerful or sophisticated integrated circuits are more susceptible to overheating and/or failure. For example, integrated circuits with a higher processing speed typically use an increased transistor density and a higher operating frequency relative to integrated circuits with a lower processing speed, and the increased transistor density and the higher operating frequency cause the integrated circuit to dissipate more heat.
Although mechanical pumps which propel fluid, fans which circulate air and similar mechanical means may be used to provide heat transfer, such mechanical means are susceptible to mechanical failure, especially at higher temperatures. For example, such mechanical means have moving parts which may be damaged by the higher temperatures and wear due to use. Further, heat transfer by such mechanical means is not optimal due to friction and other resistive forces against the moving parts. Moreover, such mechanical means typically increase the size of the assembly an unsuitable amount. The continuing increase in processing power of integrated circuits will only escalate the importance of effective cooling.
Effective cooling may be a problem in drilling operations performed to obtain hydrocarbons. To obtain hydrocarbons, a drill bit is driven into the ground surface to create a borehole through which the hydrocarbons are extracted. Typically, a drill string is suspended within the borehole. The drill bit is connected to a lower end of the drill string. The drill string extends from the surface to the drill bit. The drill string has a bottom hole assembly (BHA) located proximate to the drill bit.
Drilling operations typically require monitoring to determine the trajectory of the borehole. Measurements of drilling conditions, such as, for example, drift of the drill bit, inclination and azimuth, may be necessary for determination of the trajectory of the borehole, especially for directional drilling. As a further example, the measurements of drilling conditions may be information regarding the borehole and/or a formation surrounding the borehole and/or fluids within the formation and/or fluids within the borehole itself. The BHA may have tools that may generate and/or may obtain the measurements. The measurements by the tools may be used to predict downhole conditions and make decisions concerning drilling operations. Such decisions may involve well planning, well targeting, well completions, operating levels, production rates and other operations and/or conditions. In addition to obtaining measurements, the downhole tools may regulate power, receive commands from the surface, communicate data to the surface or another tool connected to the drill string, and control motors and/or other electromechanical devices associated with the drill string.
Integrated circuits and power semiconductor devices located in the downhole tools dissipate heat, and operation of these circuits located in the downhole tools may cease and/or may be hindered by the heat. As discussed previously, integrated circuits with a higher processing speed typically dissipate more heat; accordingly, integrated circuits used in advanced drilling technology are more susceptible to overheating and/or failure. Further, advanced drilling technology enables hydrocarbons to be obtained from environments which are deeper and hotter than previously attainable locations. The combination of increased heat dissipation by powerful and sophisticated downhole tools and the high temperature environments encountered by the downhole tools requires effective cooling to sustain operation of the downhole tools and their integrated circuits.
It is well known that of the three principal means of passive heat transfer, namely conduction, convection and radiation, only conduction is viable to transfer heat from downhole tools to the wellbore. A typical cooling system minimizes thermal resistance between the wellbore and the heat source, such as, for example, a semiconductor substrate, by using efficient heat conducting material, such as, for example, copper, aluminum and/or graphite. In addition, passive heat pipes may assist heat transfer. For example, the thermal conductivity of copper is 401 W/mK, and the thermal conductivity of graphite is 1,200 W/mK. A heat pipe may transport a heat flux of approximately 350 W/cm2 with a thermal conductivity of approximately 5,000 W/mK over a limited temperature range which extends to 150° C. However, despite the use of such heat conducting material and passive heat pipes, geometric constraints may hinder the heat transfer, and the heat transfer requirements of powerful and sophisticated downhole tools may not be met.
A heat pipe is a closed metal tube, typically mounted vertically and partially filled with a fluid, such as water. Application of heat to the lower end of the tube evaporates the water and thereby helps to cool the heat source. The upper end of the tube may be equipped with a heat sink, and the vapor may move up the tube and condense at the heat sink. The condensed fluid flows back to the lower end of the tube and may be heated and may evaporate again. The process may continue if the lower end and the upper end of the tube have different temperatures.
A problem with heat pipes is that heat pipes operate over a limited temperature range. For example, normal atmospheric pressure enables the heat pipe to maintain a heat source temperature of approximately 100° C., the temperature at which water evaporates. In addition to the temperature range of the fluid, thermal stability and thermal conductivity restrict the choice of fluid. Distilled water may be used with additives, such as, for example, acetone, methanol, ethanol and/or toluene. However, for temperatures above 100° C., the choices of suitable fluids are limited, and an increase in internal vapor pressure results in a maximum operating temperature of 150° C.
Another problem with heat pipes is orientation sensitivity. The standard heat pipe only operates in a vertical orientation because the condensed fluid must flow back to the lower end of the tube. To address this problem, capillary action may move the fluid back to the heat source. For example, a capillary structure, such as a wick, a multilayered metal mesh, or a grooved or sintered metal annulus may be connected to the interior of the tube. However, even with a capillary structure, heat pipes may lose half of their performance at 90° C. High angle wells and horizontal wells increase retrieval of the hydrocarbons and improve recovery of the area in which the wellbore is located, and heat pipes may not effectively transfer heat in such wells because of the orientation sensitivity of the heat pipes.
Yet another problem with heat pipes is failure if overheated. If the ambient temperature of the heat pipe or the temperature of the heat source exceeds a maximum operating temperature for the heat pipe, the fluid does not condense and the heat pipe will not transfer heat.
Accordingly, effective cooling is necessary to reduce equipment failure and enable increased processing power.